Engines may use various fuels, including liquid propane gas (LPG) which may be a blend of liquid propane and butane. However, on any LPG injected engine, the liquid propane retained in the fuel rail after the engine is shut down can vaporize due to residual engine heat and pressure decay in the fuel lines. The vapor in the fuel lines can significantly displace the liquid, since vapor may occupy approximately 250 times the liquid volume in the case of propane. This displacement of liquid fuel within the fuel rails can degrade subsequent engine starts due to potentially incorrect fueling.
One approach to address this situation is to purge the vapor from the fuel lines during an engine start, but before injecting fuel to the engine. However, this can lead to unacceptably long crank times, for example as long as 9 seconds, as is the case in some vehicles that take this approach.
As such, in one approach, a method for controlling a fuel system with fuel is provided. The method comprises: in response to an engine shutdown, increasing communication between a fuel rail and a fuel tank to increase boiling of fuel in the rail, and then decreasing the communication after the fuel rail cools. In this way, it is possible to advantageously utilize engine soak heat to assist in cooling the fuel rail, while at the same time enabling improved vapor purging of the fuel rail. Note that the communication may be adjusted in a variety of ways, where increasing communication may include opening a solenoid valve, or increasing opening of a solenoid valve. As such, adjusting the communication may include adjusting a degree of communication.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.